Expendable remotely piloted or programmable aircraft are well known. They are generally designed to fly to a predetermined area, to detect and to home on an enemy ground target, typically utilizing electromagnetic wave energy radiating from the target for guidance. Because such expendable aircraft require a long flight endurance, a conventional aircraft configuration is necessitated.
In the terminal guidance of such aircraft, the electromagnetic radiation sensors generally determine the angles and/or angle rates between the targets and the longitudinal axis of the aircraft in both the pitch and yaw planes. Pitch errors are generally corrected by rotating the aircraft in the pitch plane using the elevators in both "pursuit" and "proportional" guidance systems. Minimum cross coupling of motion results in the yaw plane because aircraft are generally symmetrical about the pitch plane, i.e., have equal area control surfaces on both sides of the longitudinal axis of the aircraft.
However, conventional aircraft generally cannot generate sufficient side force to change the velocity vector of the aircraft in the yaw plane. Thus, it is necessary to roll the aircraft about its longitudinal axis into the direction of the turn, and to use the horizontal component of the lift vector from the aircraft wings to turn the aircraft in the yaw plane. With a sensor fixed to the body of the aircraft, any roll about the longitudinal axis of the aircraft creates apparent errors in both pitch and yaw angles and pitch and yaw rates of change. Such errors may be significant in magnitude and may result in polarity shifts resulting in oscillation, divergence, and in mission failure. For these reasons, it is necessary to use a roll compensation circuit to calculate from the angles and rates measured by the aircraft the pitch and yaw angles and rates of change as a function of roll rate or change or in the attitude of the aircraft from a wings level or horizontal attitude. Even with roll compensation circuitry, the time lag necessarily introduced by rolling the aircraft to correct yaw errors creates a larger circular error probability than is desired.
Another problem in conventional systems is the use of a vertical gyro. Vertical gyros are very expensive. As is well known, vertical gyros become less sensitive when approaching gyro gimbal nadir or true vertical and, thus, use of a vertical gyro for roll reference limits the aircraft to shallow dive angles with the inevitable larger miss probability distances due to the geometry of such dives. Terrain blocking is also a significant possibility. If true nadir is reached, the vertical gyro cannot sense roll angle and the roll loop circuit of the guidance system may become unstable.
Still another problem is sensor accuracy. It has been a practice generally to use extremely accurate sensors so as to avoid compounding of the inaccuracies of the roll compensation circuitry with its vertical gyro.
Yet a further problem in the use of expendable remotely piloted or programmable aircraft has been the need for rapid deployment and for rapid erection when on the desired site for launching. Among the difficulties faced in such deployment is the need for storage of fuel, ordnance, and the launch rocket separately from each other and from the aircraft for obvious safety considerations.
It is accordingly an object of the present invention to obviate these and other deficiencies of known expendable remotely piloted or programmable aircraft and to provide a novel method and system.
It is another object of the present invention to provide a novel method and system in which the homing performance of an expendable remotely piloted or programmable aircraft is significantly enhanced through the elimination of rolling turns for yaw corrections during the terminal dive maneuvers.
It is still another object of the present invention to provide a novel method and guidance system for an expendable remotely piloted or programmable aircraft which eliminates the cost and complexity of roll compensation circuitry, requires less accurate sensors than conventional roll-to-turn systems, and eliminates expensive components such as vertical gyros.
It is yet another object of the present invention to provide a novel method and system for crating and for uncrating an expendable remotely piloted or programmable aircraft.
Another object of the present invention is to provide a novel method and system for rapidly and safely deploying and launching expendable remotely piloted or programmable aircraft.
Still another object of the present invention is to provide a novel expendable remotely piloted or programmable aircraft which is compact when crated yet rapidly erected.
These and many other objects and advantages of the present invention will be apparent from the claims and from the following detailed description when read in conjunction with the appended drawings.